The present invention relates to a miniature and high performance antenna applicable to a radio communication apparatus and made up of a straight antenna rod and an antenna coil or coil element.
Portable radio communication apparatuses, including hand-held telephones, are extensively used today. To enhance portability, the casing of this kind of apparatus is decreasing in size and weight. An antenna small enough to be retracted even into such a small casing has been proposed in various forms. The prerequisite with the apparatus, or bidirectional communicating means, is that it can respond to a call originated on a remote station even when the small antenna is retracted into the casing. Further, there is an increasing demand for higher antenna sensitivity. In the light of this, it has been customary to provide the apparatus with a built-in antenna in addition to the retractable antenna and use them selectively. However, the problem with this approach is that the apparatus has a complicated and bulky construction. To eliminate this problem, there has been proposed an antenna made up of a straight antenna rod and a short antenna having a loading coil. In this type of antenna, the antenna rod and short antenna are joined coaxially with each other such that only the short antenna works when the antenna rod is held in a retracted position.
However, the conventional antenna of the type described cannot achieve a desirable electric characteristic when the antenna rod is pulled out of the casing of the apparatus. Moreover, such an antenna cannot be miniature enough to promote the effective use of a space available in the casing.